The objective of this application is to develop the career of Dr. Aron Parekh as an independent researcher in the field of cancer invasion. The career development plan created by the PI and his mentor Alissa M. Weaver, M.D., Ph.D., and co-mentor Vito Quaranta, M.D., combines both the didactic and laboratory training required to build Dr. Parekh's biological knowledge and skills. The ultimate goal of the training period is to combine the PI's expertise in mechanics and mechanobiology with the mentors' expertise in molecular biology and advanced imaging techniques to equip Dr. Parekh to become a multidisciplinary researcher focused on the mechanisms of cancer cell mechanobiology. The proposed training opportunity would provide the PI protected time to gain valuable knowledge and experience in acquiring these skills to position him for a successful career in cancer invasion. The research proposal, described below, serves as the foundation of this five year career development plan and of future funding proposals. Long-term clinical outcomes are dependent on whether carcinoma cells leave the primary tumor site by migrating and invading through epithelial and adjacent stromal tissues. Cancer aggressiveness has been linked to tissue density and rigidity both in vivo and in vitro. Our laboratory has shown that mechanosensing of rigid substrates is correlated to increased extracellular matrix (ECM) degradation due to elevated activity of invadopodia, the cytoskeletal structures thought to be critical for proteolytic invasion. Therefore, these results suggest that mechanical factors such as tensile forces play an important role in driving a malignant phenotype. However, the link between biomechanics and the invasion of actual tissues remains inconclusive due to the lack of in vitro models that mimic true tissue properties, particularly those of the epithelial basement membrane (BM) and stroma. In vivo, mechanical forces generated by tumor cell packing and the desmoplastic stroma lead to increased rigidity or tension in the mammary gland and mechanical loading of the local ECM including the BM and adjoining stroma. Therefore, mechanical forces exerted on the local ECM may play an important role in regulating the invasive phenotype, but currently no studies have tested the role of ECM biomechanics under conditions that simulate the tumor microenvironment. The goal is to determine the role of these external forces in regulating cancer cell migration and invasion through the ECM. To achieve this goal, three specific aims are proposed. In Specific Aim 1, the chemical, physical, and mechanical properties of the ECM scaffold urinary bladder matrix-BM (UBM-BM) will be characterized to establish this material as a physiologically relevant in vitro ECM model. In Specific Aim 2, the hypothesis that BM tension activates a malignant phenotype that facilitates invasion will be tested by examining the penetration of UBM-BM under tension by invasive cancer cells. In contrast, Specific Aim 3 will test whether invasion through the adjacent stromal tissue occurs independent of proteolytic degradation and/or mechanosensing by utilizing the connective tissue component of UBM-BM as a model for the stroma. Dr. Parekh anticipates that these studies will yield important insight into the mechanism responsible for mechanically activating cancer cells to penetrate the BM and stroma and could open the door for novel therapeutic strategies that interfere with these processes.